I'm trying to learn the anatomy of a tail light. I know there's a bulb in there and a plastic housing but what is the definition of a taillight. Does that refer to just the bulb in the tail light assembly. Is the tail light assembly the whole plastic shell, screws and mounting clips, wiring and bulb socket, and plastic housing? Is the plastic housing you can touch from the exterior of the car surface also called the lens? Or maybe the lens is that paraboloid reflective portion the bulb is centered at its focus point?
Taillight - Generic term that could refer to any part of the assembly or the bulb. Context required. (i.e. "your taillight is cracked" = lens, "your taillight is out" = bulb, "insert the bulb into the taillight" = forward shell, etc.)
Taillight Assembly - The entire taillight, including the lens. Strictly speaking, this excludes bulbs. A manufacturer list component "taillight assembly" will not include bulbs when ordered. When on the car, however, many would refer to the bulbs as part of the assembly.
Taillight Lens - The transparent rear facing portion of the assembly.